A Methodology for Implementation of High-Efficiency Broadband Power Amplifiers With Second-Harmonic Manipulation

This brief describes a methodology for designing broadband power amplifiers (PAs) based on the manipulation of second-harmonic impedance. The proposed approach starts from the inverse class-F (F
^-1
) design specification and extends it to a family of specifications that allow achieving better than class-B performance in terms of output power and drain efficiency. It is shown that the achievable performance can be maintained over a wide frequency range reaching 57% of fractional bandwidth. As such, the proposed approach permits higher flexibility and offers relaxed matching constraints in implementing broadband high-efficiency PAs. For the experimental implementation, the proposed approach is adopted to implement a broadband PA using a 10-W gallium-nitride transistor. Peak drain efficiencies greater than 75% are measured over carrier frequencies between 500 and 900 MHz. The saturated output power levels, on the other hand, are higher than 10 W with a maximum of 13 W. Measured results are confirmed to be in good agreement with theory and simulations.